diff --git a/ext/nokogiri/extconf.rb b/ext/nokogiri/extconf.rb
index 4278dd6e46..0a771b684c 100644
--- a/ext/nokogiri/extconf.rb
+++ b/ext/nokogiri/extconf.rb
@@ -594,6 +594,10 @@ def do_clean
 append_ldflags(ENV["LDFLAGS"].split) unless ENV["LDFLAGS"].nil?
 $LIBS = concat_flags($LIBS, ENV["LIBS"])
 
+# nokogumbo code uses C90/C99 features, let's make sure older compilers won't give
+# errors/warnings. see #2302
+append_cflags(["-std=c99", "-Wno-declaration-after-statement"])
+
 # always include debugging information
 append_cflags("-g")